Why the ratio isn't the same for every rice
Different rice types absorb water at noticeably different rates, driven by shape, bran content, and starch structure, which is why one blanket ratio does not cover all of them. A short-grain white rice packs its starchy grains close together and cooks through on comparatively little added liquid; a long-grain white rice, jasmine, and basmati all sit at a middle figure; and brown or parboiled rice needs more liquid and roughly twice the time, because the bran layer left on brown rice slows how fast water reaches the starchy interior. Arborio sits furthest out at 4 parts liquid to 1 part rice, well above ordinary table rice, since its high surface starch is meant to be worked into the water gradually, not fully absorbed the way a pilaf absorbs its liquid. Wild rice is botanically a grass seed, not true rice, and it takes its own 3:1 figure and the longest simmer of the group.
USA Rice, the trade group representing the U.S. rice industry, states this variation plainly in its own cooking guidance: the "rule of thumb" is 2 parts liquid to 1 part rice by volume, but "different rice types may require slightly less or slightly more liquid" than that rule of thumb suggests. The chart below is where that qualifier gets specific, type by type.
The stovetop ratios this calculator uses
These figures come from USA Rice's own Rice Cooking Chart (usarice.com/thinkrice/how-to/how-to-cook-rice), which covers the stovetop method specifically: combine rice, liquid, and any salt or fat in a covered saucepan, bring to a boil, then reduce to a simmer for the listed time. Other USA Rice guidance gives lower ratios for sealed appliances: its foodservice playbook "Ready, Set, Rice!" puts a rice cooker at 1 cup rice to 1 cup liquid for white rice (1.25 cups for brown or converted) and a pressure cooker or Instant Pot at 1 cup rice to 1.25 cups liquid across all types, crediting both lower figures to being closed systems that lose less water than an open stovetop pot. These stovetop ratios are the starting point for either appliance, not a direct substitute for its own manual.
A separate independent check against Purdue Extension's "All About Cooking Rice" guide lines up closely but not perfectly: Purdue gives long-grain white as 1 ¾ to 2 cups liquid per cup of rice (USA Rice's 2:1 sits at the top of that range), brown rice as 2 to 2 ½ cups (USA Rice's 2.25:1 sits in the middle), and converted/parboiled rice as 2 to 2 ½ cups (same). The one place the two sources diverge is short-grain: Purdue groups medium and short grain together at 1 ½ cups, while USA Rice gives short grain its own lower 1.25:1 figure. Neither source is wrong; extension guides and industry charts each ran their own stovetop testing, and a grain's exact packing density is the kind of thing that can vary slightly by the specific rice tested. This tool uses USA Rice's more granular ten-type figures rather than Purdue's three-way grouping.
A jasmine measure and a gram conversion, worked out
1.5 cups of jasmine rice, at USA Rice's 2:1 ratio for U.S. jasmine white: 1.5 x 2 = 3 cups of water, for a 4.5-cup total once cooked (about 36 oz by weight, using USA Rice's general 8 oz-per-cooked-cup figure). Simmer time is 15 to 18 minutes, the same as any of the other 2:1 white rices.
150 grams of dry long-grain white rice, converted first to volume using USA Rice's general "1 cup dry rice is about 7 oz" figure (150 g is about 5.29 oz, or 0.756 cups): 0.756 x 2 = about 1.51 cups of water (roughly 358 mL), for an estimated 2.27 cups cooked (about 18.1 oz). The gram-to-cup step is the same regardless of rice type, since USA Rice publishes that conversion as a general average, not a per-type figure.
The math behind the cooked-yield estimate
USA Rice states one specific yield fact directly: "considering the 2:1 ratio, dry rice typically triples in volume when cooked." That is 1 part dry rice plus 2 parts absorbed liquid equaling 3 parts cooked rice, arithmetic on their own stated ratio, not a separate measurement. This calculator applies the same logic (dry rice volume plus the water it absorbs equals the cooked volume) to every ratio in the chart, so a 4:1 arborio measure is estimated at 5 parts cooked rather than a flat tripling. For the 2:1 types that reduces exactly to USA Rice's own tripling rule; for the others, it's this calculator's own extension of that logic, not a figure USA Rice publishes per type, and what actually comes out of the pot will drift a little from evaporation and how tightly the cooked grain packs.